Throughout the industry there have been increasing demands for usage of a film (namely, a functional film) having a specific function that will be formed on a base material. This is because the functional film can compensate for the performance the base material lacks. For example, on a surface of a heat exchanger and a surface of a side mirror for a vehicle may be formed with a functional film having a predetermined function, such as corrosion resistance and hydrophilicity. As one of such examples, a heat exchanger for an air conditioner will be described as follows.
An air conditioner is an electric appliance having a function of controlling a desired temperature and humidity of a predetermined room. Such an air conditioner typically uses a freezing cycle and the freezing cycle, and includes a compressor, an evaporator, an expansion valve and a condenser. The evaporator and the condenser are types of heat exchangers, and they include a tube to enable flow of a refrigerant therein and a cooling fin installed in a tub. In other words, the refrigerant flowing in the evaporator and the condenser heat-exchange heat with ambient air. The evaporator may absorb the heat while evaporating the refrigerant and the condenser may emit the heat while condensing the refrigerant.
However, when a surface temperature of the heat exchanger falls below a dew point, air is condensed and a water droplet is generated on a surface of the heat exchanger. If the water droplet generation is severe, the water droplet is frozen to become a frost. The water droplet and/or the frost generated on the surface of the heat exchanger might cause several problems. For example, the water droplet and/or frost might reduce a heat exchange area to thereby deteriorate the heat exchanging performance of the heat exchanger. Also, the water droplet and/or frost might produce a kind of flow resistance, to increase the power required by a fan used to generate flow of air to the heat exchanger. Accordingly, it is preferable that the water droplet and the like are not condensed on the surface of the heat exchanger. To solve the problem, it has been attempted that the surface of the heat exchanger has hydrophilicity to cause flow of the condensed water droplet down the surface of the heat exchanger.
Meanwhile, a heat exchanger, especially, a heat exchanger installed in an outdoor unit of the air conditioner is exposed directly to an outside whereby corrosion might occur as usage time passes. Such a phenomenon might be severe when the heat exchanger is installed in salty conditions such as near a sea shore. Accordingly, it has been proposed that application of a corrosion resistance coating should be performed on a surface of the heat exchanger.
In addition, as the usage time passes, fungus and bacteria inhabit a surface of a heat exchanger and a bad smell might be generated, which might present a sanitary problem. However, the heat exchanger is typically mounted in an indoor or outdoor unit and it is not easy to clean the heat exchanger. As a result, it has been proposed that anti-bacteria/anti-fungi (hereinafter, antibiotic) coating should be provided on the surface of the heat exchanger.
To solve the problems mentioned above, it has been proposed that a functional film should be coated on a surface of a heat exchanger. For example, chrome (Cr+6) rust-proofing is performed to a surface of a heat exchanger to provide corrosion resistance to the surface of the heat exchanger and silicate coating is performed on the chrome rust-proofed surface of the heat exchanger to provide hydrophilicity to the surface, such that the surface of the heat exchanger may have corrosion resistance and hydrophilicity. This method is typically called as “Pre-coated material (namely, PCM). However, such a PCM method has a disadvantage of environmental pollution caused by the chrome and another disadvantage of aging that gradually deteriorates hydrophilicity with the passage of time.
To solve those problems of the PCM method, it is proposed that titanium should be coated on the surface of the heat exchanger. As one of proposals, Korean Patent No. 10-2006-32565 is disclosed. That is, to gain a hydrophilic surface, titanium is coated on a surface of a heat exchange through plasma reaction. In this instance, it is difficult to use titanium in the plasma reaction as it is, because the evaporation point of titanium is thousands of degrees. Accordingly, a titanium compound, in other words, a titanium precursor is made to use in the plasma reaction easily. Up until the present time, titanium isopropoxide (Ti(OC3H7)4) is used as the titanium precursor. In this instance, to supplement corrosion resistance, hexamethyldisiloane (HMDSO) is coated before the titanium thin film is formed. After that, titanium isopropoxide is used to perform plasma deposition as the titanium precursor. Also, to gain antibiotic function, a precursor is made of a predetermined material such as copper or cobalt that is known to have the antibiotic function and the precursor is used for plasma deposition. In other words, the coating for gaining corrosion resistance, the coating for gaining hydrophilicity and the coating for gaining antibiosis are sequentially performed in that prior art.
Meanwhile, an apparatus having a functional film formed by using conventional plasma enhanced deposition and a method for controlling the same will be described as follows.
First of all, a base material is cleaned in a cleaning chamber. After that, the cleaned base material is deposited in a plasma reaction chamber for plasma reaction and a functional film is generated. The base material having the functional film formed therein is re-cleaned in the cleaning chamber. In other words, according to the conventional plasma enhanced deposition, pre-cleaning, functional film deposition and post-cleaning are performed in various chambers. Also, when forming the functional film, a corrosion resistance layer, a hydrophilicity film and an anti-biotic film are formed in different chambers, respectively. As a result, the conventional plasma enhanced deposition has to include independent chambers to perform each of the processes and each of the processes may be performed in each of the different chambers independently. Accordingly, the apparatus and control method for forming the functional layer might be disadvantageously complex.
Also, the conventional plasma enhanced deposition using conventional functional film forming technology has proposed that the functional film be formed on a raw material before manufacturing a product. In other words, it has been proposed that the functional film should be formed on the surface of the sheet shaped material before the sheet shaped material having the functional film formed thereon is processed to manufacture a radiation fin of the heat exchanger.
However, this has a problem of failing to manufacture the product having the functional film formed in all parts thereof. Also, the functional film is not formed on an area processed from a raw material, for example, a front sectional area, so that corrosion might be partially generated in the front sectional area. Accordingly, reliability of the product might be deteriorated.
To solve the problem, Korean Patent No. 10-2003-0078455 discloses a plasma enhanced chemical vapor deposition apparatus to form a functional film on a product itself.
In the conventional plasma enhanced chemical vapor deposition apparatus, a product is conveyed to a carrier to form the functional layer. An electric power is supplied to the product via the carrier in contact with a pair of rollers. Accordingly, the power supply is quite complex and the electric power is supplied via the rollers so that reliability of power supply might be deteriorated disadvantageously. Also, the functional film is formed on the carrier and efficiency might be deteriorated disadvantageously.
Moreover, the product, that is, the heat exchanger is transferred while being hung on the carrier. Accordingly, the transfer structure is complex and the electric power fails to be supplied between the carrier and the heat exchanger stably and this might cause a problem.
A single electrical connection point has to be formed in the heat exchanger and a uniform functional film cannot be formed in the heat exchanger entirely.
Meanwhile, in the conventional plasma enhanced chemical vapor deposition apparatus, it might not be easy to load and unload the heat exchanger. Accordingly, the work process happens to be inefficient and it might be difficult to install and separate the carrier.